Process and apparatus for treating metal melts



Aug. 22, 1961 H. FElCHTlNGER PROCESS AND APPARATUS FOR TREATING METALMELTS Filed June 26, 1959 2 Sheets-Sheet 1 MVP.

6 ATTORNEY 2,997,386 PROCESS AND APPARATUS FOR TREATING METAL MELTSHeinrich Feichtinger, 16 Holzbrunnenstrasse,

Schafllrausen, Switzerland Filed June 26, 1959, Ser. No. 823,227 Claimspriority, application Switzerland June 27, 1958 15 Claims. (Cl. 75-93)This invention relates to a process and apparatus for treating metalmelts for the purpose of degasification or formation of certaingas-metal compounds therein which influence the primary structure.

Heretofore it has been the practice to add reducing or alloyingsubstances to a melt that flows into a closed vessel under vacuum. Thesealing of the compartments that contain a vacuum with respect to theoutside atmosphere is difiicult to eifect in practice and requires aconsiderable expenditure in packings and vacuum pumps to obtain andmaintain the vacuum, so that processes, where a vacuum is used, can onlybe applied under considerable diflicultiesin the rough steel milloperation, and the resulting increase in the price of the end productmakes the use of these methods in many cases unprofitable.

In general, however, there is a tendency today in metallurgy to degasifymetals by means of a vacuum so that a great number of processes triedout in the last years are carried out with equipment which is suitablefor the production and maintenance of a vacuum, as is the case in theabove described methods. I have found, however, in my investigationsthat practically the same and often better results can be obtainedwithout using a vacuum for the degasification of melts.

The disadvantages resulting from the application of a vacuum areeliminated by the invention since it offers the prerequisite for asimpler and safer method where there is no necessity for vacuum pumpsand vacuum-tight seals. This is achieved by carrying out the reaction ofthe melt with suitable substances in an atmosphere which has a slightover-pressure with regard to the outside atmosphere. The substancesreacting with the melt are not added to the melt in ground or moltenform, as it is the case in the known vacuum methods, but in the form ofa continuous wire strip whose feed can be regulated simply and reliably.

The total arrangement thus obtained has the advantage that the apparatusin which the treatment is effected can be used with normal ladles, asthey are used in steel works, using only a simple sand cup-packingbetween the apparatus and the ladle. Compared to other devices thatrequire a vacuum, the apparatus and the ladle occupy only little spaceand have a relatively low weight, so that both can be brought directlyunder the casting spout of a melting unit by means of a crane and, onthe other hand, can be transported directly to the casting plant afterthe ladle has been filled with the treated metal. The metal remainsconstantly under a protective gas atmosphere until it is cast, whichprotects it against undesired absorption of gas from the atmosphere.Methods that use a vacuum, on the other hand, must always insert theladle to be filled with the treated melt into a closable vessel which isdifiicult to handle because of its vacuum-packing against the outsideatmosphere; besides is heavy and has a great volume. Because of its sizeand its connection to the vacuum pumps, this vessel cannot be broughteasily to the various molds, so that the ladies inserted in thesevessels must be removed again from the vessels after they have beenfilled with the treated melt, and are exposed to the influence of theoutside atmosphere.

These methods where the melt is introduced into a vac- Patented Aug. 22,1961 uum chamber have not only the great disadvantage con-' nected withthe generation and maintenance of a vacuum, but the melt jet enteringthe chamber begins immediately to divide when entering the vacuumchamber, which renders the introduction of the reaction substances inthe form of a wire or strip difiicult, since the latter can only beintroduced properly when it is hit directly by the flowing jet of melt.

It is, however, a principal object of this invention to introduce thesubstances reacting with the melt, in the form of a wire or strip whichis conducted exactly into the entering melt. The melt added incontrollable amounts by means of a simple feed gravitates into aconfinedchamber where it is combined with the metallic substance of thewire or strip without the necessity of complicated vacuum gates ordosing devices.

The process can be carried out preferably in this way that the metalwire or strip penetrating into the melt consists of partly or completelyevaporating material, so that it evaporates in a sort of explosion whenpenetrating into the melt; the jet of the entering melt being divided sothat the atmosphere prevailing in the chamber or the atmosphere formedby the metal vapor reacts over a large surface with the melt to betreated.

Since the melt can be torn into small particles within the reactionchamber without the application of a vacuum, and the method according tothe invention represents a considerable progress with regard to othermethods, where melts are introduced in troughs which are staggered insteps so that the melt flows like a cataract from one step to the other,and the additives are introduced in the vacuum chamber of the varioussteps, these methods are not suitable for an intensive treatment ofmelts with reaction substances, since the surface action between thereaction substance and the melt is not great enough. Eiforts havetherefore been made to introduce these substances, which have not beencompletely reacted, again in one or several successive stages into thevacuum chamber of these steps, to make the utilization of these reactionsubstances more economical. The thorough reaction and degasification ofthe melt with the reaction substances is achieved, however, in a muchsimpler way and in a smaller space with the method according to thisinvention, since the melt is introduced into a chamber that is sealedfrom the outside atmosphere, in which there is a highly reducingatmosphere, this reducing atmosphere being formed by means of a metalWire or strip of easily evaporating metals, which is fed penetratinglyinto the jet of the melt entering the sealed chamber. It is possible toadd other alloying elements together with the metal wire or strip forforming the reducing atmosphere, which are to be protected against theinfluence of the outside atmosphere. It has been found expedient to addalloying elements mixed with magnesium and other reducing agents in theform of a wire orstrip, the wire or strip cohering with mixed ground oralloyed substances within a tubular envelope which consists ofmagnesium, aluminum, steel or iron, sheet or other suitable metals. inthose cases where the melt must be heated, the introduced vw're or stripconsists partly or entirely of substances, as they are used, forexample, in alumino-thermy, which react on contact with the jet of theliquid melt, generating heat. The composition is preferably so selectedthat there is also a reduction of the melt in addition to the generationof heat. According to the process of the invention it is also possibleto introduce wires or strips simultaneously with the entering melt indifferent levels or from different directions. Thus, for example, amagnesium Wire can be introduced from one side, from another direction astrip containing the alloying elements, to be added, and from a thirddirection a strip for increasing the temperature.

It is also possible to advance these wires and strips with a fixedlyadjusted feed. Preferably a feed is selected by means of rollers whichpermit any desired advance motion ofthe wire or strip over an infinitelyvariable gear. It is also possible to regulate the feed overautomatically controlled auxiliary devices. Thus, for example, the feedof the wire or strip for increasing the temperature of the melt can becontrolled over a temperature measuring device. In this case the currentof a thermocouple element, for example, which dips into the treatedmelt, or which is heated by the atmosphere in the reaction chamber, actsover relays on the feeding device. Instead of the thermo-couple elementthe relays can also be actuated by a pressure element as a transmitter.

Embodiments for carrying out the process according to the invention arerepresented in the attached drawing, in which:

FIG. 1 is an embodiment of the invention in which the treated meltenters into an open ladle; and

FIG. 2 shows a modified form of my invention in which the treatedreaction device proper is attached on a lid closing the ladle.

The process is principally suitable for treating diiferent metal melts.The method and the apparatus shown in FIG. 1 consists of a compositeiron and steel melt. The steel melt to be tapped from a melting unit,for example, an arc furnace, is discharged slowly into the upper ladle1, so that the ladle 1 remains filled with an approximately constantlevel of liquid steel 10 during the entire process. At the same time, ora little earlier, the cock 5, leading from an inert gas supply, isopened so that an inert gas atmosphere flows into the chambers 3 and 11,as the gas flows from the steel cylinder 6 into the chamber 3. This flowof inert gas displaces the noninert gases found in the chambers 3 and1-1. The overpressure thus generated escapes over the annular re ceiver14, over the line 15, and over the relief valve 16 to the outsideatmosphere. As soon as an inert gas a mosphere has been formed in thechambers 3 and 11, the stopper 2 is opened so that the melt 10 can flowinto the reaction chamber 3, which is formed by the walls 4. At the sametime a conveyor drive 7 is started so that the metal wire or strip 8moves through the guide 9, in the reaction chamber 3, against theentering jet 17, penetrating into the latter. The metal wire or strip 8melts during the penetration and mixes with the entering metal at 17.This metal wire or strip 8 consists of partly or completely evaporatingsubstances, for example, magnesium, and the jet of the entering melt istorn by the spontaneous formation of vapor into small particles whichcan enter into interaction with the gaseous and vaporous atmospherebecause of their large surface. The gas source contained in steelcylinder 6 is argon or any other inert gas. It is also possible toreplace this source by a protective gas generator. This treated meltpasses through a constricted annular chamber 18, and discharges into afunnel-shaped extension 19, and flows finally into the channel 11 whichis formed by the walls 29, and terminates in the ladle 21. The stopper 2is controlled by operating handle 22 while the stopper 24 is controlledby the operating handle 23. The metal strip 8 consists of thin wires orstrip, for example, magnesium wire, and it is preferably rolled up as aroll 25, and inserted in a housing 26 coupled in the tubular member 9 at27, so that it is protected against steel splashes, for example, whichmight ignite it. This housing 26 starts at 27, close to the tubularmember 9. The delivery rate of the feed means or rollers 7 can beadjusted in a suitable manner by an infinitely variable gear (not shown)to any desired speed. It is thus possible to treat the steel, which hasfirst been analyzed for its gas content, with an accurately adjustedamount of reacting additives, for example, magnesium. It is alsopossible to use the apparatus without the stopper 2. In this case thecock and the metal strip 8 are actuated as hereinbefore described.Moreover, it is also possible to carry out the process completelywithout any additional supply of an inert gas atmosphere or an inert andreducing gas atmosphere, respectively, being formed automatically in thechamber 3, by the entering mel-t on the one hand and by the introducedmetal strip on the other hand.

In the embodiment of the device for carrying out the process accordingto the invention represented in FIG. 2, an upper ladle 30 is again usedwhich can be closed with a stopper 31. Before the metal melt isintroduced into the chamber 32, the valves 33 and 34 are opened 50 thatboth the ladle chamber 35 and the reaction chamber 32 are filled withinert gases or with gases which are not harmful for the reactionprocess. The over-pressure generated in this case escapes either throughthe annular chamber 36, or through the relief valve 38, inserted in thelid 39. The lid can be sealed with a sand cup-packing 40, against theladle 41. As soon as an inert gas, or any other desired gas atmospherehas been formed in the chambers 32 and 35, the stopper 31 is opened sothat the metal melt -42 flows into the chamber 32. At the same time, theconveyor 43 is put in motion, so that the metal strip 44- is movedthrough the tubular member 45. At 47 a packing is preferably provided sothat the overpressure generated in the chamber 32 cannot escape throughthe tubular member 45, thus overheating the conveyor or feed means 43 aswell as the metal wire or strip 4-4. After the melt has passed thereaction chamber 32 it arrives in the collecting funnel 48, and over aconstriction in the ladle 41. The ladle 41 is provided with stopper 50and an operating handle 51 controls the opening and closing thereof. Thestopper 31 is provided with operating handle 52. Reference character 53designates the gas source for inert gas. As soon as the ladle is filledwith the treated melt it is possible to transport it, together with theentire equipment, entirely to the casting mold by means of a crane. Thelid 39 can remain closed so that the treated melt 49 is protectedagainst undesired gasification during the transport. During the castingit is also possible to fill the mold first with an inert gas. Besides, aprotective tube filled with inert gas can be arranged between thecasting mold and the ladle 41 so that it is possible to cast the treatedmelt, which has an optimum of gas content and gas metal compound,without uncontrolled gasification. Particularly, because of theseproperties and characteristics, the process according to this inventionhas great advantages over the known processes where the treated meltcannot be protected during the transport against gasification, and it isparticularly suitable for mloying those elements which are to beprotected against the influence of an uncontrolled atmosphere.

In the operation of the method and apparatus of my invention, thechamber 3 is sealed from the outside atmosphere and an over-pressure ismaintained in the inner atmosphere of the chamber allowing the inneratmosphere to escape to the outer atmosphere without the latterpenetrating into the chamber. The metallic substance, which may bemagnesium, or an alloy consisting of aluminum, magnesium or manganese,is fed through the tubular member 9 or 45 which may be formedfrom sheetmetal such as steel, iron, aluminum, or magnesium, adapted to readilycombine with the metallic melt which gravitates downwardly from theupper ladle 1 into the chamber 3 where the metallic substance combineswith the metallic melt and evaporates and greatly divides the melt anddegasifies the same. The feed means 7 are located within the housing 26for advancing the wire or strip 8 from a coil 25 through the tubularmember 9. The composite melt with the metallic substance combinedtherein is collected in the ladle 21 or 41 for discharge under controlof stopper 24 or 50.

While I have described my invention in certain of its preferredembodiments I realize that modifications may be made and I desire thatit'be understood that no limi- '5 tations upon my invention are intendedother than may be imposed by the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is as follows:

1. A process for treating metal melts which comprises: introducing ametal melt in the form of a jet of molten metal into a treatment chambersubstantially closed from the outside atmosphere, introducing into saidtreating chamber a stream of inert gas, whereby there is established insaid treating chamber, an inner atmosphere of said inert gas,simultaneously allowing said inner atmosphere of inert gas to escapeinto the outer atmosphere, without permitting the latter to penetrateinto said inner chamber, whereby there is maintained in said treatingchamber a slight overpressure of said inert gas, feeding at acontrollable, continuously variable rate of speed, a strand of metalliccomposition, directly into said jet of molten metal, whereby said jet issplit and disrupted without the necessity of requiring a vacuum.

2. A process for treating metal melts as set forth in claim 1 in whichsaid strand of metallic composition which is fed into the melt ispartially evaporated therein.

3. A process for treating metal melts as set forth in claim 1 in whichsaid strand of metallic composition which is fed into the melt isspontaneously evaporated at approximately the position the melt entersthe chamber for dividing melt.

4. A process for treating metal melts as set forth in claim 1 in whichsaid strand of metallic composition which is fed into the melt iscomposed of magnesium.

5. A process for treating metal melts as set forth in claim 1 in whichsaid strand of metallic composition which is fed into the melt consistsof an alloy of aluminum, magnesium, and manganese, operating to degasifythe melt.

6. Apparatus for treating metal melts which comprises: a treatmentchamber substantially closed to the outside atmosphere, conduit meansfor introducing into said treating chamber a stream of inert gas, meansfor allowing escape of gas from said chamber into the outer atmosphereand for substantially preventing penetration of outer atmosphere intosaid chamber, means for introducing molten metal into said treatmentchamber, and means for feeding at a controllable, continuously variablespeed, a continuous strand of metallic composition through said conduitmeans directly into said molten metal as it is introduced into saidchamber, said metallic composition reacting with the melt.

7. Apparatus for treating metal melts as set forth in claim 6 in whichsaid conduit means is formed from sheet metal and provides asubstantially air-tight seal at its outer end for the introduction ofthe strand of metallic composition while excluding the outer atmospheretherefrom.

8. Apparatus for treating metal melts as set forth in claim 6 in whichsaid conduit means is formed from steel and provides a substantiallyair-tight seal at its outer end for the introduction of the strand ofmetallic composition while excluding the outer atmosphere therefrom.

9. Apparatus for treating metal melts as set forth in claim 6 in whichsaid conduit means is formed from iron and provides a substantiallyair-tight seal at its outer end for the introduction of the strand ofmetallic composition while excluding the outer atmosphere therefrom.

10. Apparatus for treating metal melts as set forth in claim 6 in whichsaid conduit means is formed from aluminum and provides a substantiallyair-tight seal at its outer end for the introduction of the strand ofmetallic composition while excluding the outer atmosphere therefrom.

11. Apparatus for treating metal melts as set forth in claim 6 in whichsaid conduit means is formed from magnesium and provides a substantiallyair-tight seal at its outer end for the introduction of the strand ofmetallic composition while excluding the outer atmosphere therefrom.

12. Apparatus for treating metal melts as set forth in claim 6 in whichthe metallic composition constitutes introduced through said conduitmeans contains reducing elements for combination with the metal melt.

13. Apparatus for treating metal melts as set forth in claim 6 in whichthe strand of metallic composition introduced through said conduit meansalso constitutes means which effects the heating of the melt.

14. Apparatus for treating metal melts as set forth in claim 6 in whichthe metallic composition constitutes a strip and wherein there is ahousing attached to the exterior end of said conduit means containing areel on which said strip is coiled and in which said means for feedingsaid metallic composition is located within said housing and engagessaid strip for feeding the strip through the conduit means.

15. Apparatus for treating metal melts as set forth in claim- 6 in whichthe metallic compositon constitutes a wire and wherein there is ahousing attached to the exterior end of said conduit means containing areel on which said wire is coiled and in which said means for feedingsaid metallic composition is located within said housing and engagessaid wire for feeding the wire through the conduit means.

References Cited in the file of this patent UNITED STATES PATENTS2,675,308 Millis et a1. Apr. 13, 1954 2,837,790 Rozian June 10, 19582,882,571 Easton Apr. 21, 1959

1. A PROCESS FOR TREATING METAL MELTS WHICH COMPRISES: INTRODUCING AMETAL MELT IN THE FORM OF A JET OF MOLTEN METAL INTO A TREATMENT CHAMBERSUBSTANTIALLY CLOSED FROM THE OUTSIDE ATMOSPHERE, INTRODUCING INTO SAIDTREATING CHAMBER A STREAM OF INERT GAS, WHEREBY THERE IS ESTABLISHED INSAID TREATING CHAMBER, AN INNER ATMOSPHERE OF SAID INERT GAS,SIMULTANEOUSLY ALLOWING SAID INNER ATMOSPHERE OF INERT GAS TO ESCAPEINTO THE OUTER ATMOSPHERE, WITHOUT PERMITTING THE LATTER TO PENETRATEINTO SAID INNER CHAMBER, WHEREBY THERE IS MAINTAINED IN SAID TREATINGCHAMBER A SLIGHT OVERPRESSURE OF SAID INERT GAS, FEEDING AT ACONTROLLABLE, CONTINUOUSLY VARIABLE RATE OF SPEED, A STRAND OF METALLICCOMPOSITION, DIRECTLY INTO SAID JET OF MOLTEN METAL, WHEREBY SAID JET ISSPLIT AND DISRUPTED WITHOUT THE NECESSITY OF REQUIRING A VACUUM.